The present invention relates to a numerical control system and, more particularly, a shaft control method in the numerical control system applied in the case that each movable shaft is moved by a plurality of motion modules.
The numerical control system executes the numerical control process based on the machining program and applies the machining to the work in pursuance of the command by driving the machine tool according to result of the process.
FIG. 9 is a block diagram showing a hardware of the numerical control system in the prior art. In FIG. 9, 10 is the numerical control system. The microprocessor (CPU) 12 is the control center of the overall numerical control system 10, and reads the system program stored in the ROM 13 via the bus line 11, and executes the control of the numerical control system 10 according to this system program. The temporary computation data, the display data, etc. are stored in the RAM 14. The machining program, the tool data, various parameters, etc. are stored in the CMOS 15. The CMOS 15 is always backed up by the battery (not shown), and thus the stored data are held as they are when the power supply of the numerical control system 10 is turned OFF.
The interface 16 is the interface for the external apparatus, and the external apparatus 17 such as the floppy disk drive (FD), the personal computer (PC), or the like is connected to the interface 16. The external apparatus 17 such as the floppy disk drive (FD), the personal computer (PC), or the like can input/output the machining program, the tool data, various parameters, etc. into/from the numerical control system 10.
The graphic control circuit (CRTC) 18 converts the digital data such as present positions of respective shafts, the alarm, the machining program, various parameters, image data, etc. into the image signals and then outputs them. This image signals are supplied to the CRT 19 on the operation board 22 on the numerical control system 10, and then displayed on the CRT 19. The keyboard control portion 20 receives the data from the keyboard 21 on the operation board 22 and then transmits the data to the microprocessor 12.
The shaft control circuit 23 receives the moving commands of respective shafts from the microprocessor 12, and then outputs such moving commands of respective shafts to the servo amplifier 25. The servo amplifier 25 receives these moving commands, and then drives the servo motors 34 of respective shafts installed onto the machine tool 30. The pulse coder (not shown) to sense the position is built in the servo motor 34, and the position signal is fed back from this pulse coder as the pulse train. The velocity signal can also be generated by F/V (frequency/velocity)xe2x80x94converting this pulse train. In FIG. 9, the feedback lines of these position signals and the velocity feedback lines are omitted. The servo motors 34 are provided to the X-axis, the Y-axis, the Z-axis, and the C-axis respectively.
The spindle control circuit 26 receives the commands such as the spindle rotation command, the spindle orientation command, etc. and then outputs the spindle velocity signal to the spindle amplifier 27. The spindle amplifier 27 receives this spindle velocity signal and then causes the spindle motor 33 to rotate at the instructed rotation speed. Also, the spindle amplifier 27 positions the spindle at a predetermined position in response to the orientation command.
The programmable machine controller (PMC) 28 is built in the numerical control system 10, and controls the machine based on the sequence program that is constructed in the ladder format. In other words, the programmable machine controller (PMC) 28 converts the M command, the S command, and the T command, which are instructed by the machining program, into the signals required for the sequence program on the machine side, and then outputs the signals from the I/O unit 29 to the side of the machine tool 30. These output signals operate various devices on the machine side. Also, the programmable machine controller (PMC) 28 receives the signals from the limit switch on the side of the machine tool 30, the switches on the machine operation panel, etc., and then transmits the signals which are subjected to the necessary process to the microprocessor 12.
In recent years, the small and high-performance product that employs the linear motor, or the like as the motion module can be supplied. Also, the numerical control system can attain the extremely high speed in the process with the higher performance of the microprocessor 12, and thus can simultaneously control the good many shafts. For example, as shown in FIG. 10, the machine having the configuration in which respective movable shafts (Z axis, C axis) are moved by a plurality of motion modules has been invented. In the case of FIG. 10, the configuration in which respective movable shafts in the Z axis and the C axis are moved by a plurality of motion modules is employed.
FIGS. 11A to 11C shows the example of the configuration in which the linear movable shaft is moved by a plurality of motion modules. FIG. 11A is the example of the configuration in which a plurality of motion modules 31 are arranged with respect to one movable shaft in series with the moving direction of the movable shaft. Since respective motion modules 31 can apply the force to the movable shaft 32 in the directions indicated by the arrow, the movable shaft 32 can be moved in the directions indicated by the arrow.
FIG. 11C is the example of the configuration of the multipolar linear DC motor. This linear DC motor has the configuration that the armature (mover) 44, which corresponds to the primary side of the linear motor, is moved on the field (stator) 45, in which the N-pole and the S-pole of the magnet that correspond to the secondary side of the linear motor are alternatively arranged.
FIG. 11B is the example of the configuration in which the linear movable shaft constructed by the linear motor shown in FIG. 11C is moved by a plurality of motion modules. In other words, a plurality of armatures (movers) 44 that correspond to the primary side of the linear motor are fixed to the linear movable shaft 32, and the field (stator) 45 that corresponds to the secondary side of the linear motor is provided below the armatures (movers) 44. The linear movable shaft 32 can be moved by the thrust, that a plurality of armatures (movers) 44 receive from the field (stator) 45, in the direction indicated by the arrow.
Also, FIG. 12A is the example of the configuration in which a plurality of motion modules 31 are arranged with respect to one movable shaft in parallel with the moving direction of the movable shaft. In this case, like FIG. 11A, since respective motion modules 31 apply the force to the movable shaft 32 in the direction indicated by the arrow, the movable shaft 32 can be moved in the direction indicated by the arrow.
FIG. 12B is the example of the configuration in which the linear movable shaft constructed by the linear motor shown in FIG. 11C is moved by a plurality of motion modules. In other words, a plurality of armatures (movers) 44 that correspond to the primary side of the linear motor are fixed to the linear movable shaft 32, and in this case the fields (stators) 45 that correspond to the secondary side of the linear motor are provided below the armatures (movers) 44 to correspond to the armatures (movers) 44 respectively. The linear movable shaft 32 can be moved by the thrust, that a plurality of armatures (movers) 44 receive from the corresponding field (stator) 45 respectively, in the direction indicated by the arrow.
FIG. 13 is the example of the configuration in which the rotational movable shaft is moved by a plurality of motion modules. A plurality of motion modules 31 are arranged with respect to one rotational movable shaft in the circular direction of the movable shaft. The movable shaft 32 can be rotated by applying the force to the movable shaft 32 from respective motion modules 31 in the direction indicated by the arrow.
The motion module is the servo mechanism as shown in FIG. 14. The moving command is output from the motion-module control device 24 to the servo amplifier 25. The servo amplifier 25 receives this moving command to drive the servo motor 34. The position sensor 35 is fitted to the servo motor 34, and thus the position signal is fed back from the position sensor 35 as the pulse train. The configuration consisting of the servo motor 34 and the position sensor 35 corresponds to the motion module 31.
In case a large torque is needed to move the movable shaft, the large-size motor is required to generate the large torque. Meanwhile, in the case that one movable shaft is moved by a plurality of motion modules, the necessary motor can be constructed by a plurality of small-size motors if a sum of torques of respective motors may provide the necessary torque. If doing so, the occupied space of the motor can be considerably reduced rather than the case where the large-size motor is employed.
Also, as shown in FIGS. 12A and 12B, it is possible to move the movable shaft by applying the force uniformly to the movable shaft, and also it is possible to move the movable shaft with good balance. In particular, if the movable shaft is large, the deflection of the movable shaft, etc. can be prevented in contrast to the case where the movable shaft is moved by one motion module, like the prior art. Thus, the employment of a plurality of motion modules is effective to prevent the deflection of the movable shaft.
The normal numerical control system is constructed on the premise that each movable shaft is moved by a single motion module respectively. Also, in the machining program of the numerical control system, the machining operation is defined by defining the motion of each movable shaft. For this reason, there is the problem that, in the numerical control system in the prior art, the machining program cannot deal with the multi-shaft control such that each movable shaft is constructed by a plurality of motion modules.
In order to overcome this problem, there is proposed the system in which the moving command issued to the movable shaft is distributed to respective motion modules that correspond to the movable shaft, by providing the special circuit to respective motion modules constituting the movable shaft. However, in this system, there is the problem that the special distributing circuit must be provided individually according to the configurations of the movable shaft and the motion modules.
In the normal numerical control system, the machining must be interrupted when the failure is caused merely in one motion module. This is because each movable shaft is moved by a single motion module respectively in the normal numerical control system and thus it is difficult to move the movable shaft because of the failure of the motion module. In this case, the motion module has the relatively high failure occurring rate in the numerical control system. Thus, if the system is constructed by a large number of motion modules, the failure occurring rate becomes high as the overall system. As a result, there is the problem that the reduction in the reliability of the overall system is bought about.
The present invention has been made to overcome above problems, and it is an object of the present invention to provide a shaft control method in the numerical control system that is capable of employing a normal machining program, which provides the definition of the machining operation, as it is by defining a motion of each movable shaft even in the situation that each movable shaft consists of a plurality of motion modules.
Also, it is another object of the present invention to provide a shaft control method in the numerical control system that is capable of controlling the movable shaft by providing the redundancy to the motion modules which cause the movable shaft to move even when the failure occurs in some motion modules.
In order to achieve this object, a numerical control system in which one movable shaft is moved by a plurality of motion modules, comprises a storing means for storing a machining program for the movable shaft, a storing means for storing a movable-shaft correlation table that converts a moving command given in unit of the movable shaft based on the machining program into individual moving commands of the motion modules, and a motion-module controlling means for controlling the motion modules based on the moving commands converted by the movable-shaft correlation table.
Also, a numerical control system further comprises a setting means for setting correlations between the movable shaft and a plurality of motion modules into the movable-shaft correlation table.
Also, a numerical control system further comprises a failure sensing means for sensing a failure of the motion modules, a servo-off execution commanding means for providing a servo-off command that executes servo-off of a defective motion module when the failure is sensed, and a motion-module disconnecting means for disconnecting the defective motion module.
Also, the servo-off execution commanding means executes the servo-off of the defective motion module and brings the defective motion module into a free-running state.
Also, a numerical control system further comprises a disconnectable shaft number setting table for setting a number of disconnectable motion modules every movable shaft that is moved by a plurality of motion modules, and an alarm outputting means for outputting an alarm when a number of the motion modules, which are disconnected since the failure is caused therein, exceeds a value that is stored in the disconnectable shaft number setting table.
Also, a shaft control method in a numerical control system comprising the steps of obtaining a moving command given in unit of the movable shaft based on a machining program, converting the moving command into individual moving commands of a plurality of motion modules, which move the movable shaft, based on a movable-shaft correlation table, and controlling respective motion modules based on individual converted moving commands of the motion modules.